设函数f(x)和g (x)在[a,b]上存在二阶导数,且 ''(x)neq -|||-0, (a)=f(b)=g(a)=g(b)=0. 试证:-|||-(1)在开区间(a,b )内 (x)neq 0;-|||-(2)在开区间(a,b )内至少存在一点ξ,使-|||-dfrac (f(xi ))(g(xi ))=dfrac (f''(xi ))(g''(xi ))